Touchy

Touchy

A surface-mount solderingkit for touch and play

Schematics and assembly information

We've designed a simple touch and scroll board based on Silicon Labs' EFM8SB1Sleepy Bee microcontroller. The microcontroller comes in a QSOP24 package that has a 0.625 mm pitch, the distance between the centre of one pin to the centre of the next. This kit could be a challenge to solder, but we like challenges, and we hope that you do too! (We have a QSOP/SMD practice board available.)

The circuit

There are six capacitive-touch 'buttons' and one scroll-wheel. Six pins are connected to LEDs (active-low) and also to a 2.54 mm header. The rest of the pins are also routed out to the header, as are ground and a possible external power input to replace the on-board coin cell 3V battery.

Use the information on the schematics to help solder the kit correctly. Note a couple of things:

The 1μF and 0.1μF 0805 capacitors look identical, and unlike resistors, do not have value markings on them. We've marked the packaging that the 1μF capacitor comes in with a black line.

There is a 'solder-blob' jumper that connects the Vext pin with the battery power. If you jump that pin, make sure not to have both the battery and the external power on at the same time since this causes contention and leads to problems.

Software and programming

You'll need to use Silicon Labs' Simplicty Studio in order to edit and compile the design for the microcontroller. For programming, you have two options:

USB-to-serial programming through the UART factory bootloader. The chip comes with a UART bootloader already loaded for us. There is a somewhat clunky process to upload converted HEX designs (the output of the complication process) to the chip via this interface.

Silicon Labs' C2 programmer. 'C2' is the primary programming and debug interface of the chip. Silicon Labs sells C2 programmers for about £27. These are too expensive for a one-off project, but if you're going to do some more development for this board or these types of microcontrollers, it might be worth the investment.

Oliver Coles

This project is dedicated to the memory of Oliver Coles. Oli died in June 2016. I (Saar) did not know him that well; in fact, we've only met once in my office almost two years ago. He was humble and passionate about his work, which was on the outskirts of engineering and art, similar, but much more so than what I do at Boldport. It was impressive. After our meeting we occasionally continued to discuss mutually interesting projects over email, the latest being a particularly ambitious video stitching project using FPGAs he was working on.

Oli was a Boldport Club member, and the first to tell me that the Tiny 'engineer superhero' emergency kit saved him, twice! (I gave him one of the original kits when he visited.) This apparently trivial remark meant a lot to me. I now regret not having more interactions with Oli, and saddened that we won't get to experience more of his creations.

I went to Oli's wake at a North London pub a few weeks after his death. It was good to hear and see more about him and his work, and know that he had many loving friends and family. This dedication is my small way of thanking Oli for his work.

Further information

Touchy is an open source design, as is most of our work. You can find the design files for the hardware and packaging at our GitHub repository. You can edit the design files using our own PCB design open source software, PCBmodE.

Touchy project was Project #7 of the Boldport Club. Community contributions such as build logs and software are available on our community site. If you'd like to purchase a kit, become a member and add one to your order through the shop.